Filament support structure



Aug. 27, 1957 w. M. COUCH, JR 2,804,567

FILAMENT SUPPORT STRUCTURE Filed April 28, 1954 2 Sheets-Sheet l IN V EN TOR.

FIG. 2

ATTORN EY WILLIAM M. COUCH, JR.

Aug. 27, 1957 w. M. COUCH, JR 2,804,567

FILAMENT SUPPORT STRUCTURE Filed April 28, 1954 2 Sheets-Sheet 2 29 INVENTOR. W WIL LIAM M. COUCH, JR.

FIG.3.

ATTORNEY United States Patent 2,804,567 FILAMENT SUPPORT STRUCTURE" William M. Couch, Jr., NewC anaan, Conn., assignor'to Machlett Laboratories, Incorporated, Springdale, Conn, a corporation of Connecticutv Application April 28, 1954, SerialNo. 426,227

7 Claims. (Cl. 313276) This invention relates to a novel filament support-structure for use in an electron tube. More specifically, this invention relates to a support structure for an intermediate supported portion of a filament which is to be maintained at a potential different from the potentials at the respective ends of the filament.

In many electron tube applications it is desirable to have all of the strands of the filament in series rather than having several strands in parallel. For instance, where it is desirable to have a relatively low current supplied to the filament, it is often more convenient to feed this current-into a single strand or a number of strands arranged in series than to divide it into the. parallel paths furnished by filament strands arranged in parallel;

Inapplications where it isdesirable to have the strands ofthe filament in series rather than in parallel, the problem of supporting these strands assumes importance. Because the voltage drop is spread out over a longer length of filament, the supports for intermediate portions ofthe elongated filament are at different potentials from one anotherand from the ends of the filament. Because of the ditference'in the potentials at thevarious supported points, the supports, including supports for the filament ends, must be insulated from one another.

In the-prior art it has been possible to support a series type filament at various points alongits length using relatively flimsy support structures. In modern electron tubes, however, interelectrode and inter-support spacings are often quite small. Therefore, it is desirable to have a sturdy supporting structure for each part of the fila ment so that there is no opportunity forthe filament or its supports to short to its adjacent electrode. This invention provides such a sturdy support for the filament.

It has become common to support the ends of a parallel squirrel cage type filament on parallel planar decks which may be made extremely rugged. This invention-involves the use of at least one planar deck in connection with a single strand or series type filament. In the preferred form of this invention a pair of these deck members mount rod support members for supporting the ends of a series'type filament strand. In addition, a support for an intermediate portion of the filament is mounted on one of the decks. This support preferably consists of a pair of aligned rods separated by an insulator. One of the rods is afiixed to one of the decks and the other of the rods is affixed to a portion of the filament.

In the preferred form of the present invention the ends of the rods adjacent the insulator are terminated in cup-like receptacles for receiving the opposite ends of the insulator. Preferably this insulator is a ceramic which may be soldered to the cup-like members using ceramic-to-metal' soldering techniques.

Fora better understanding of the present invention reference is made. to the following drawings:

Fig 1 is a vertical sectionof an electron tube structure employing the presentinvention.

Fig. 2 is across-sectionalview. of he structure of. Fig. 1

A 2,804,567 Patented Aug. 27, 1957 t we 2, taken at line- 2-2 of-Fig. 1, but also showing part of the grid ring,

Fig. 3 is a'vertical section of the tube structure of Fig. 1 rotated about the tubes major axis.

Referring to the drawings, an electron tube structure is illustrated which is typical of tube structures which may employ the present invention. In the structure illustrated there is an anode 10, a grid generally designated 11 and a filament 12. The anode 10 is preferably composed of a cup ofhigh conductivity material, which cup may beexternally cooled in some conventional manner. Collar 13 and mounting ring 14 are aflixed vacuum tight to the anode. Collar 13 is preferably composed of some metal whichwill seal relatively easily to the glass envelope 15. Tubular metallic shield 16 is aifixed at the lip of the anode cup on the inside thereof to extend above the glass-to-metal seal between members 13 and 15 so that the seal may be protected from bombardment. The glass envelope 15 is closedat that end opposite the endsealed; to the anode by a dish-type press 18; This press'has a plurality of tubular necks to which are sealed small metallic collars 19 which are composed of glass-sealing metal. Collars 19 in turn support and are sealed vacuum tight to supporting rings 20. Supporting rings20 are then, in turn, sealed vacuum tight to heavy highlyconductive terminal posts 21-, 22 and 23. Posts 21 support-the opposite sides of the grid structure. Posts 22 and 23 support'the respective ends of the filament. Mounting posts 21, 22 and 23 are all ruggedly constructed so that they will maintain their positions despite severe heating withinthe envelope and rough mechanical handiing of the tube structure.

Posts 21 are mounted diametrically opposite one another on grid ring 25 by screws 26 or the like. Also held in place by the screws 26 is grid support collar 27. Grid support collar 27 has a tubular flange which supports grid support rods 28. Rods 28 are in general straight and parallel to the tubes axis, but they do have bends adjacent their supported ends in order to increase their mounting diameter to conform with grid ring 27. The grid rods 28 are all terminated in end cap 29 to which they are aifixed, as by Welding. Around the grid rods are wrapped a plurality of turns of a helix of refractory metal wire 30.

Filament decks 31 and 31a are composed of planar members of relatively heavy material for increased Iigidity. These decks are mounted in parallel planes generally perpendicular to the axis of the tube and to the filament support posts 22 and 23. They are afi'ixed respectively to the filament support posts 22 and 23 preferably by brazing, and, in order to provide added strength in the joints, the filament support posts are provided with studs 22a and 23a, respectively, which studs snugly fit holes in the deck members 31 and 31a, respectively. Deck 31 mounts filament support rod 33 which is alfixed perpendicularly to the plane of deck 31. Deck 31a mounts filament support rod 34 which is afiixed perpendicularly to the plane of deck 31a. Rod 33 is afl'ixed to one end of filament 12 by means of a clip 35, Rod 34 is fixed to the other end of the filament by support tab 36. The intermediate portion of the filament in this instance is broken and the broken ends are supported on a pair of tabs 38 carried by intermediate support rod 39. Accordingly, this filament is divided into two V- shaped, or hairpin portions which are separate from one another. The filament, of course, could be one piece and of W-shape, and it could be connected to rod 39 of the support in some other manner than by tabs 38.

The support for the intermediate filament portion is composed of rods 39 and 43 and insulator 41. Rod, 39 is terminated in a cup-like member. 40- which snugly engages insulator member 41 which is preferably a ceramic which may be soldered to cup member 40 using some conventional ceramic-to-metal soldering technique. The other end of ceramic insulator member 41 is engaged by a cup member 42 which is similar to cup 40 and which is preferably similarly soldered in place. Cup 42 terminates one end of rod 43 whichis itself terminated perpendicular to deck 31. Rod 43 is preferably engaged in a hole in deck 31 and affixed there by brazing or other appropriate means. Thus, the support provided by members 39, 40, 41, 42 and 43 is itself solid and is,

in turn, mounted upon a solid structure.

The term deck as used herein refers to any planar surface whether a surface of a sheet metal member supported on a rod or a tubular support, the square end of heavy walled tubing, a ring penetrating the sidewalls of a vacuum envelope, or any other planar surface no matter how supported.

mediate support members, each similar to the one here illustrated and either mounted on the same deck or on separate decks. The supports need not have rod members, however, e. g., the deck itself may be affixed to the bottom of the ceramic engaging cup or a tubular post rather than a rod support may be employed. No

matter what type of support is provided, however, the deck type mounting provides a sturdy rugged support which enables close interelectrode spacings with minimum danger of shorting.

Many modifications of the present invention will occur to those skilled in the art. All modifications within the terms of the claims are intended to be within the scope and spirit of the invention.

I claim: 1. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament, a pair of rigid metal rods each having one end conductively connected to a respective end of the filament, a pair of metal members each carrying a respective rod, the members being fixedly secured to the inner ends of the filament terminal posts whereby the filament and rods are conductively connected to the terminal posts, and supporting means on one of the metal members supporting an intermediate portion of the filament, the supporting means being insulated from its supporting member by an insulator.

2. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament, a pair of rigid metal rods each having one end conductively connected to a respective end of the filament, a pair of metal members each carrying a respective rod, the members being fixedly secured to the inner ends of the filament terminal posts whereby the filament and rods are conductively connected to the terminal posts, and a third 'rod mounted on one of the members in the plane of said first rods and supporting an intermediate portion of the filament, the third rod being insulated from its supporting member by an insulator.

3. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation. to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament, a pair of rigid metal rods each having one end conductively connected to a respective end of the filament, a pair of metal discs each carrying a respective rod, the discs being fixedly secured to the inner ends of the filament terminal posts whereby the filament and rods are conductively connected to the terminal posts, and supporting means mounted on one of the discs supporting an intermediate portion of the filament, the supporting means comprising a pair of rodlike supporting members aligned in spaced end-to-end relation and connected together by an insulator, one of the rodlike members being fixedly atfixed to the disc on which it is mounted and the other rodlike member being connected to the intermediate portion of the filament.

4. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament, a pair of rigid metal rods each having one end conductively connected to a respective end of the filament, a pair of metal discs each carrying a respective rod, the discs being fixedly secured to the inner ends of the filament terminal posts whereby the filament and rods are conductively connected to the terminal posts, and supporting means mounted on one of the discs supporting an intermediate portion of the filament, the supporting means comprising a pair of rodlike supporting members aligned in spaced end-to-end relation and connected together by an insulator, said rodlike members at the ends thereof adjacent the insulator terminating in cup-like members which snugly receive the adjacent portions of the insulator.

5. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament, a pair of rigid metal rods each having one end conductively connected to a respective end of the filament, a pair of metal discs each carrying a respective rod, the discs being fixedly secured to the inner ends of the filament terminal posts whereby the filament and rods are conductively connected to the terminal posts, and supporting means mounted on one of the discs supporting an intermediate portion of the filament, the supporting means comprising a pair of supporting members aligned in spaced end-to-end relation and connected together by an insulator, said rodlike members at the ends thereof adjacent the insulator terminating in cup-like members which snugly receive the adjacent portions of the insulator, the major portion of said insulator being of a diameter substantially larger than the diameter of the rodlike members and physically presenting an insulating buffer between the rods and rodlike members.

6. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament having two wires connected in series, each wire having two spaced portions overlying each other, a pair of rigid metal rods each having one end conductively connected to one end of a respective filament wire, a pair of metal discs each carrying a respective rod, the discs being fixedly secured to the inner ends of the filament terminal posts whereby the filament wires and rods are conductively connected to the filament posts, and supporting means mounted on one of the discs in a common plane with said rods, and comprising two rodlike members aligned in spaced end-to-end relation and connected together by an insulator, one of said rodlike members being fixedly -aflixed to the disc on which it is mounted and the other rodlike member being connected to the other ends of the filament wires.

7. An electron tube comprising an envelope, an anode carried by the envelope, a cathode within the envelope in predetermined spaced relation to the anode, and cathode filament terminal posts carried by and extending through the envelope, said cathode comprising a filament having two wires arranged in series, each wire having two spaced portions overlying each other, a pair of rigid metal rods each having one end conductively connected to one end of a respective filament wire, a pair of metal discs each carrying a respective rod, the discs being fixedly secured to the inner ends of the filament terminal posts whereby the filament wires and rods are conductively connected to the filament posts, and supporting means mounted on one of the discs in a common plane with said rods, and

comprising two rodlike members aligned in spaced endto-end relation and connected together by an insulator, one of said rodlike members being fixedly afiixed to the disc on which it is mounted and the other rodlike member being connected to the other ends of the filament wires, the major portion of the insulator being of a diameter substantially larger than the diameter of the rodlike members and physically presenting an insulating buffer between the rods and rodlike members.

References Cited in the file of this patent UNITED STATES PATENTS 1,766,460 Schwerin June 24, 1930 1,931,987 Holst et a1 Oct. 24, 1933 2,444,483 Wing July 6, 1948 

